The present invention relates to the field of telescopes and more particularly to mirrors used in such telescopes.
In a regular, Newtonian telescope, there is typically a telescope tube at the end of which is a curved silvered mirror, usually made out of glass. The mirror is supported on three points which are attached to the end of the telescope tube. This allows adjustment of the mirror in one plane. The edge of the mirror is stabilized by an edge support, and safety clips retain the mirror in case the telescope should accidently point below the horizon. This kind of three point support is useful for mirrors up to about 8 inches in diameter. Smaller mirrors can be made relatively thin but larger mirrors must be made thicker in order to reduce sagging. In larger mirrors, therefore, support is provided by more than three points. At each of the three main support points there are bars or triangles which spread the force applied by the mirror over a larger area. Consequently, the number of support points is usually a multiple of three.
Spreading of the force is important because without something that will spread the force, the mirror will deform thus affecting focusing, adjustment of the entire telescope and impairing image quality and communications gain. The problems with this kind of mirror mounting are that the supports must be loose to avoid stressing the mirror and degrading its performance. Also, the retaining clips obscure part of the mirror, introduce unwanted edge diffraction defects and may damage coatings on the mirror. Systems for larger mirrors are mechanically complex, requiring low friction bearings at the linkage points and, when the back adjustment points are in the shape of an equilateral triangle, collimation of the mirror is made more complex by the interaction between all these adjustment points. For a discussion of three and nine point support of telescope mirrors see articles by Toshimi Taki, published in the September, 1994 issue of Sky and Telescope from pages 84 through 87 and the April, 1996 issue from pages 75 through 77. Examples of complex support systems for telescope mirrors can be seen in U.S. Pat. No. 4,632,523, issued to Knohl on Dec. 30, 1996 and U.S. Pat. No. 3,182,552, issued to Audy on May 11, 1965.
Development of a mounting system for telescope mirrors which will allow larger, thinner mirrors to be permanently mounted in a telescope without the need for edge clips and edge supports represents a great improvement in the field of telescope design and satisfies a long-felt need of the astronomer.